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Probability
Kinds of Probability Terms modified by Probability Selected AbstractsUPPER BOUNDS ON THE MINIMUM COVERAGE PROBABILITY OF CONFIDENCE INTERVALS IN REGRESSION AFTER MODEL SELECTIONAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2009Paul Kabaila Summary We consider a linear regression model, with the parameter of interest a specified linear combination of the components of the regression parameter vector. We suppose that, as a first step, a data-based model selection (e.g. by preliminary hypothesis tests or minimizing the Akaike information criterion , AIC) is used to select a model. It is common statistical practice to then construct a confidence interval for the parameter of interest, based on the assumption that the selected model had been given to us,a priori. This assumption is false, and it can lead to a confidence interval with poor coverage properties. We provide an easily computed finite-sample upper bound (calculated by repeated numerical evaluation of a double integral) to the minimum coverage probability of this confidence interval. This bound applies for model selection by any of the following methods: minimum AIC, minimum Bayesian information criterion (BIC), maximum adjusted,R2, minimum Mallows' CP and,t -tests. The importance of this upper bound is that it delineates general categories of design matrices and model selection procedures for which this confidence interval has poor coverage properties. This upper bound is shown to be a finite-sample analogue of an earlier large-sample upper bound due to Kabaila and Leeb. [source] PROBABILITY-BASED OPTIMAL DESIGNAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2008J. M. McGree Summary Optimal design of experiments has generally concentrated on parameter estimation and, to a much lesser degree, on model discrimination. Often an experimenter is interested in a particular outcome and wishes to maximize in some way the probability of this outcome. We propose a new class of compound criteria and designs that address this issue for generalized linear models. The criteria offer a method of achieving designs that possess the properties of efficient parameter estimation and a high probability of a desired outcome. [source] PROBabilities from EXemplars (PROBEX): a "lazy" algorithm for probabilistic inference from generic knowledgeCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 5 2002Peter Juslin Abstract PROBEX (PROBabilities from EXemplars), a model of probabilistic inference and probability judgment based on generic knowledge is presented. Its properties are that: (a) it provides an exemplar model satisfying bounded rationality; (b) it is a "lazy" algorithm that presumes no pre-computed abstractions; (c) it implements a hybrid-representation, similarity-graded probability. We investigate the ecological rationality of PROBEX and find that it compares favorably with Take-The-Best and multiple regression (Gigerenzer, Todd, & the ABC Research Group, 1999). PROBEX is fitted to the point estimates, decisions, and probability assessments by human participants. The best fit is obtained for a version that weights frequency heavily and retrieves only two exemplars. It is proposed that PROBEX implements speed and frugality in a psychologically plausible way. [source] Calculation of Posterior Probabilities for Bayesian Model Class Assessment and Averaging from Posterior Samples Based on Dynamic System DataCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2010Sai Hung Cheung Because of modeling uncertainty, a set of competing candidate model classes may be available to represent a system and it is then desirable to assess the plausibility of each model class based on system data. Bayesian model class assessment may then be used, which is based on the posterior probability of the different candidates for representing the system. If more than one model class has significant posterior probability, then Bayesian model class averaging provides a coherent mechanism to incorporate all of these model classes in making probabilistic predictions for the system response. This Bayesian model assessment and averaging requires calculation of the evidence for each model class based on the system data, which requires the evaluation of a multi-dimensional integral involving the product of the likelihood and prior defined by the model class. In this article, a general method for calculating the evidence is proposed based on using posterior samples from any Markov Chain Monte Carlo algorithm. The effectiveness of the proposed method is illustrated by Bayesian model updating and assessment using simulated earthquake data from a ten-story nonclassically damped building responding linearly and a four-story building responding inelastically. [source] The probabilities of sex offender re-arrestCRIMINAL BEHAVIOUR AND MENTAL HEALTH, Issue 2 2003Roderic Broadhurst Associate Professor Background Estimates of the probabilities of re-arrest for sex offenders apprehended in Western Australia between April 1984 and December 1994 are reported. Population and method Of the 116,151 distinct male persons arrested for the first time from 1984,94, 2785 were identified with at least one sex offence. Subjects on average were followed up for 5.7 years and assessed by criminal record, Aboriginality, bail status, age, occupation and penal intervention. Three criteria, rearrest for any, repeat sex or a violent offence are used to summarize the ,careers' of sex offenders. Results Overall ultimate probabilities of rearrest for any offence were 0.61, for a repeat sex offence 0.33 and for a violent offence 0.51. Probabilities of re-arrest for non-Aboriginal offenders were lower for all definitions. Younger offenders, Aborigines and those with prior arrest for non-sex offences had higher probabilities for any or violent rearrest but older offenders tended to have higher probabilities of repeat sex offending. Community supervision and imprisonment significantly reduced the ,rate' or speed of re-arrest. Discussion Actuarial risk assessments for low-probability high-consequence events such as dangerous recidivism are useful for identifying groups with a high probability of rearrest, assisting management of these groups and evaluating penal interventions. Copyright © 2003 Whurr Publishers Ltd. [source] Probabilities as Similarity-Weighted FrequenciesECONOMETRICA, Issue 4 2005Antoine Billot A decision maker is asked to express her beliefs by assigning probabilities to certain possible states. We focus on the relationship between her database and her beliefs. We show that if beliefs given a union of two databases are a convex combination of beliefs given each of the databases, the belief formation process follows a simple formula: beliefs are a similarity-weighted average of the beliefs induced by each past case. [source] Pricing Loans Using Default ProbabilitiesECONOMIC NOTES, Issue 2 2003Stuart M. Turnbull This paper examines the pricing of loans using the term structure of the probability of default over the life of the loan. We describe two methodologies for pricing loans. The first methodology uses the term structure of credit spreads to price a loan, after adjusting for the difference in recovery rates between bonds and loans. In loan origination, it is common practice to estimate the probability of default for a loan over a specified time horizon and the loss given default. The second methodology shows how to incorporate this information into the arbitrage free pricing of a loan. We also show how to derive an estimate of the credit spread due to liquidity risk. For both methodologies, we show how to calculate a break,even credit spread, taking into account the fee structure of a loan and the costs associated with the term structure of marginal economic capital. The break,even spread is the minimum spread for the loan to be EVA neutral in a multi,period setting. (J.E.L.: G12, G33). [source] Modelling Probabilities of DevaluationsECONOMICA, Issue 281 2004Gabriela Mundaca I show why, when the realized rates of depreciation within the exchange rate band are regressed on a given information set and conditioned on (ex post) actual no realignment (à la drift adjustment), a ,peso problem' is still encountered. The reason is that the frequency of realignments in the data need not be the same as the frequency of the (even small) subjective probabilities that a realignment may take place. I suggest an alternative approach to solve the peso problem and provide consistent estimates. My estimates of the expected realignment rates are greater than the ones obtained using the drift adjustment method. [source] Probabilities of alcohol high-risk drinking, abuse or dependence estimated on grounds of tobacco smoking and nicotine dependenceADDICTION, Issue 6 2003Ulrich John ABSTRACT Aims, To estimate probabilities of alcohol high-risk drinking, alcohol abuse and alcohol dependence on grounds of smoking-behaviour related variables and single nicotine dependence criteria. Design, Cross-sectional population-based study. Setting, Adult population of a region in north Germany. Participants, Cigarette smokers (n = 2437) among a random sample of 4075 females and males aged 18,64, drawn in 1996. Measurement, Smoking, nicotine dependence according to the Diagnostic and Statistical Manual of Psychiatric Disorders (DSM-IV) and the Fagerström Test for Nicotine Dependence (FTND); increasing alcohol-related harm (ARH): high-risk drinking, DSM-IV alcohol abuse, remitted and current alcohol dependence diagnosed by the Composite International Diagnostic Interview (CIDI). Findings, Having smoked 30 cigarettes or more per day, onset of smoking at the age of 17 or younger, nicotine dependence and single nicotine dependence criteria revealed odds ratios higher than 4.0 for alcohol dependence. For alcohol dependence, a logistic regression model showed an increased odds ratios for male gender, smoking for 25 years or more, no attempt to quit or cut down, continuation of smoking despite problems, craving for nicotine, withdrawal experience 1 day or longer, smoking first cigarette in the morning 5 minutes or less after waking. The probability of increasing ARH was more likely in males, smokers for 25 years or more, no attempt to quit or cut down, continuation of smoking despite problems and smoking first cigarette in the morning 5 minutes or less after waking. Conclusions, Gender and single nicotine dependence criteria show particularly high probabilities of alcohol dependence and increasing ARH. Interventions need to take these connections into account. [source] Probabilities of activation of seismic faults in critical regions of the Aegean areaGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2004C. B. Papazachos SUMMARY Properties of the accelerating seismic crustal deformation pattern and of the intermediate-term seismic quiescence pattern have been combined to identify faults in the Aegean area (34°N,43°N, 19°E,30°E) that have a considerable probability of generating strong earthquakes (M, 6.4) during the next 5-yr period. Eight groups of such faults have been identified, and the probability of each fault being activated during this time period has been estimated. Three of these groups are located in southern Greece (Hellenic Arc), two in central Greece (East Central Greece, Ionian Islands), two in northwestern Turkey and one in the area of the borders of Albania, Greece and the Former Yugoslav Republic of Macedonia. The importance of these results for intermediate-term seismic hazard assessment is discussed. [source] Screening for depression and anxiety: correlates of non-response and cohort attrition in the Netherlands Study of Depression and Anxiety (NESDA)INTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 4 2009Willem Jan Van Der Veen Abstract A major problem in the analysis of attrition of cohorts in studies on mental health problems is that data on those who do not participate at the outset of a study are largely unavailable. It is not known how underlying psychopathology affects the first stages of screening where non-response and selectivity are usually highest. This article presents results of one of the centres of the Netherlands Study of Depression and Anxiety (NESDA), a longitudinal study aimed at describing the long-term course and consequences of depression and anxiety disorders. The aim is to describe the different ways of attrition during the first NESDA-wave in a cohort of patients aged 18,65 years of the Registration Network Groningen and to analyse whether attrition is related to gender, age and psychopathology as recorded in general practice. The attrition of the study cohort (n = 8475) was highest during the first stages, eventually leading to a population of 169 patients only who participated in the full NESDA-programme. Probabilities of transition from one stage of the screening process to the next were regressed on selected background variables using binary logistic regression. Correlates of participation were being female and being older (>40). Psychopathology was an important variable in the formation of the initial sample cohort, but only had a weak influence on patient response to the screening questionnaire. Study design factors had a stronger impact on the changing composition of the cohort at each screening stage compared to patient factors. Copyright © 2009 John Wiley & Sons, Ltd. [source] Detection, survival rates and dynamics of a cryptic plant, Asclepias meadii: applications of mark-recapture models to long-term monitoring studiesJOURNAL OF ECOLOGY, Issue 2 2009Helen M. Alexander Summary 1Analysis of population trajectories is central to assessing risk in populations of conservation concern. In animal studies, researchers realize that probabilities of detection of individuals are often less than one. Plants can also escape detection due to dormancy, herbivory, or observer error, but such information is rarely incorporated into population studies. 2We monitored a population of Asclepias meadii, a rare long-lived prairie perennial. Despite standardized methods, numbers of observed plants fluctuated greatly from 1992 to 2006. Individual plants often had periods of 1,5 years between initial and final sighting when no stems were found. To determine the actual population trajectories, we estimated rates of survival and population growth using mark-recapture models. We also estimated initial and resighting probabilities of detection. In 2007, we repeated surveys to identify reasons for low detection probabilities. 3We estimated 95% annual survival and a population growth rate of 1.023. Probabilities of initial detection were low (typically from 0.120 to 0.311 depending on prairie burn treatment), whereas average probability of detection for marked plants was 0.728. 4Comparisons of survival estimates from 15- and 8-year data sets revealed that survival estimates decline in the final years of a multi-year period, probably due to heterogeneity in encounter histories. 5By conducting three different surveys in 2007, we found that both herbivory over a multiple-week period and observer error contributed substantially to gaps in detection. 6Synthesis. Probabilities of detection that are less than one complicate interpretation of population dynamics, whether of mobile animals or inconspicuous plants. Our work illustrates three general points that could apply to many plant population studies: (i) mark-recapture models may provide insights on vital rates and population trajectories despite the extreme variability in count data that can arise because of low detectability, (ii) probabilities of initial detection can be quantified and can be considerably less than probabilities of resighting, and (iii) repeated surveys can help researchers determine the degree to which dormancy, herbivory, or observer error contribute to low probabilities of detection. Consideration of these points can improve the design and analysis of monitoring programs. [source] Probabilities of heart donors arising within specified times for child recipientsJOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 1-2 2007John C Galati Aim: To determine the availability of donor hearts for children of different blood group and weight needing urgent heart transplantation. Methods: Data maintained by the Australia and New Zealand Organ Donor Registry 1989,2004 were analysed to determine the frequency of donation. Probabilities of suitable donor availability within 10, 20, 30, 40, 60, 90 and 180 days were estimated using a Poisson model with the assumptions that traditional ABO blood compatibilities applied, suitable donors were 0.8,4.0 times the recipient's body weight (BW) and suitable adult donors were aged <40 years. Results: Probabilities of suitable donor availability increase with passage of time from 10 to 180 days and decrease with competition from other needful recipients. Maximum suitable donor availability occurs for children of all blood groups at body weight 20 kg. The probabilities of a donor heart arising within 40 days (maximum safe duration of extracorporeal membrane oxygenation support locally available for young children) for this recipient body weight according to blood group is 0.89, 0.85, 0.73, 0.67 (AB, A, B, O). Probabilities for recipients of BW 3 kg and 60 kg respectively are 0.16, 0.14, 0.10, 0.09 (AB, A, B, O) and 0.66, 0.61, 0.47, 0.42 (AB, A, B, O). Conclusion: Expectation of suitable heart donation arising within 40 days for needful recipients in Australia is low for infants (probability <0.3), moderate for small children (probability 0.5,0.9) and modest for large children (probability 0.4,0.7), with variation at all body weights according to blood group and waiting time. [source] Dynamics in Central European near-natural Abies-Fagus forests: Does the mosaic-cycle approach provide an appropriate model?JOURNAL OF VEGETATION SCIENCE, Issue 2 2008Rafat Podlaski Abstract Question: The mosaic-cycle concept of forest dynamics dominates in Central Europe. According to this concept intermediate-scale disturbances only accelerate the forest break-up under existing cycles of forest development. Is such an approach correct, or should new developmental cycles be elaborated for intermediate-scale disturbances? Location: Near-natural Abies alba - Fagus sylvatica forests in the ,wiétokrzyski National Park in Central Poland. In these forests intermediate-scale disturbances occurred between 1970 and 1990. Methods: Data were collected twice in areas surrounding 212 permanent sample points (in 1994 and 2004). Two increment cores were taken from 259 sample Abies trees. The effect of intermediate-scale disturbances on radial increment of Abies was assessed. Probabilities of stand transition during a 10-year period between individual stages and phases of development of the mixed forest were calculated. The development stages and phases were arranged into hypothetical succession series of successive changes. Results: In 1994 70 stands and in 2004, 47 stands representing stages and phases containing the older generation formed by trees > 100,150 years were found. Also, in 1994 142 and in 2004, 165 stands representing stages and phases containing the younger generations only, formed by trees < 100-150 years, were recorded. Stages and phases containing only younger generations do not occur in the existing forest development cycle which does not consider the influence of intermediate-scale disturbances separately. Two developmental cycles, which take into account the presence of the older generation and the younger generations only (under conditions of the occurrence of intermediate-scale disturbances), are proposed. Conclusion: The mosaic-cycle concept of forest dynamics can be used to analyse the dynamics of Central European near-natural mixed-species forests, but new developmental cycles should be elaborated for intermediate-scale disturbances. [source] Decision analysis: an aid to the diagnosis of Whipple's diseaseALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2006M. OLMOS Summary Background Diagnosis of Whipple's disease, a rare systemic infection affecting predominantly the small bowel, is based on the identification of the bacterium Tropheryma whipplei. Aims To make explicit diagnostic uncertainties in Whipple's disease through a decision analysis, considering two different clinical scenarios at presentation. Methods Using appropriate software, a decision tree estimated the consequences after testing different strategies for diagnosis of Whipple's disease. Probabilities and outcomes to determine the optimum expected value were based on MEDLINE search. Results In patients with clinically-predominant intestinal involvement, diagnostic strategies considering intestinal biopsy for histology (including appropriate staining) and the polymerase chain reaction testing for bacterial DNA were similarly effective. In case of failure of one procedure, the best sequential choice was a polymerase chain reaction analysis after a negative histology. Of the five strategies tested for cases with predominant focal neurological involvement, the stereotaxis cerebral biopsy evidenced the highest expected value. However, using quality-adjusted life-years considering the morbidity of methods, intestinal biopsy for PCR determination was the best choice. Conclusions In patients with Whipple's disease having predominant digestive involvement, intestinal biopsies for histology should be indicated first and, if negative, a bacterial polymerase chain reaction determination should be the next option. Although the molecular polymerase chain reaction assessment of cerebral biopsies has the highest diagnostic yield in neurological Whipple's disease, its associated morbidity means that analyses of intestinal samples are more appropriate. [source] On the Use of Imprecise Probabilities in ReliabilityQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 3 2004F. P. A. Coolen Abstract Theory of imprecise probability generalizes classical probability theory, by assigning to each event an interval instead of a single number. In this paper, we briefly discuss this generalization and some recently suggested applications of imprecise probabilities in reliability. We also comment on challenges for research and applications. Copyright © 2004 John Wiley & Sons, Ltd. [source] The Urban Complex: Scalar Probabilities and Urban ComputationARCHITECTURAL DESIGN, Issue 5 2010Anthony Burke Abstract Guest-editor AnthonyBurke redefines complexity in relation to the city as ,a dynamic and luminal organisational condition "growing at the edge of chaos"' and in so doing shifts our understanding of urban trauma as an event intrinsic to the contribution of the metropolis rather than external to it. Copyright © 2010 John Wiley & Sons, Ltd. [source] Comparison of a self-administered tampon ThinPrep test with conventional pap smears for cervical cytologyAUSTRALIAN AND NEW ZEALAND JOURNAL OF OBSTETRICS AND GYNAECOLOGY, Issue 3 2005Mardi BUDGE Abstract Aim: To assess a self-administered tampon specimen as an alternative method of detecting cytological abnormalities and its acceptability in comparison with a conventional Papanicolou (pap) smear. Design: Comparative observational study. Setting/population: Two hundred and seventeen women were recruited from the colposcopy clinic of an outer urban public teaching hospital and from sexual health clinics at suburban and major metropolitan hospital clinics. Methods: Participants inserted and immediately withdrew a tampon, then placed it into a vial of ThinPrep PreservCyt fluid. This was analysed by a local private pathology laboratory. Results were compared to a pap smear performed the same day or within the previous 6 months. All women with an abnormal result (tampon or pap smear) underwent a colposcopy, with or without biopsy as necessary. Participants completed a questionnaire after performing the tampon test. Outcome measures: Probabilities of tampon test detecting (i) a high grade abnormality (pHG), (ii) any cervical intraepithelial neoplasia (CIN) changes (pCINany), and (iii) any abnormalities (pabn) compared to the conventional pap smear and, if abnormal, compared to the biopsy taken at colposcopy. Acceptability of the tampon test and conventional pap smear were also measured. Results: Probabilities of the tampon test compared to pap smear: pabn sensitivity 33%, specificity 89%, PPV 59%, NPV 73%; pCINany sensitivity 23%, specificity 97%, PPV 71%, NPV 79%; pHG sensitivity 19%, specificity 98%, PPV 63%, NPV 89%. Acceptability for tampon test was 91.21% and for pap smear, 45.85%. Conclusions: Although the self-administered tampon ThinPrep method is a poor detector of cervical abnormalities compared to pap smear, it is highly acceptable to women. It has a relatively good negative predictive value (NPV). Our study suggests that if a more acceptable, sensitive method of cervical screening was found, which removed some of the existing barriers to conventional pap testing, screening rates for cervical cancer may improve. [source] Site Occupancy Models with Heterogeneous Detection ProbabilitiesBIOMETRICS, Issue 1 2006J. Andrew Royle Summary Models for estimating the probability of occurrence of a species in the presence of imperfect detection are important in many ecological disciplines. In these "site occupancy" models, the possibility of heterogeneity in detection probabilities among sites must be considered because variation in abundance (and other factors) among sampled sites induces variation in detection probability (p). In this article, I develop occurrence probability models that allow for heterogeneous detection probabilities by considering several common classes of mixture distributions for p. For any mixing distribution, the likelihood has the general form of a zero-inflated binomial mixture for which inference based upon integrated likelihood is straightforward. A recent paper by Link (2003, Biometrics59, 1123,1130) demonstrates that in closed population models used for estimating population size, different classes of mixture distributions are indistinguishable from data, yet can produce very different inferences about population size. I demonstrate that this problem can also arise in models for estimating site occupancy in the presence of heterogeneous detection probabilities. The implications of this are discussed in the context of an application to avian survey data and the development of animal monitoring programs. [source] Estimating Transition Probabilities from Aggregate Samples Plus Partial Transition DataBIOMETRICS, Issue 3 2000D. L. Hawkins Summary. Longitudinal studies often collect only aggregate data, which allows only inefficient transition probability estimates. Barring enormous aggregate samples, improving the efficiency of transition probability estimates seems to be impossible without additional partial-transition data. This paper discusses several sampling plans that collect data of both types, as well as a methodology that combines them into efficient estimates of transition probabilities. The method handles both fixed and time-dependent categorical covariates and requires no assumptions (e.g., time homogeneity, Markov) about the population evolution. [source] Capture,Recapture When Time and Behavioral Response Affect Capture ProbabilitiesBIOMETRICS, Issue 2 2000Anne Chao Summary. We consider a capture,recapture model in which capture probabilities vary with time and with behavioral response. Two inference procedures are developed under the assumption that recapture probabilities bear a constant relationship to initial capture probabilities. These two procedures are the maximum likelihood method (both unconditional and conditional types are discussed) and an approach based on optimal estimating functions. The population size estimators derived from the two procedures are shown to be asymptotically equivalent when population size is large enough. The performance and relative merits of various population size estimators for finite cases are discussed. The bootstrap method is suggested for constructing a variance estimator and confidence interval. An example of the deer mouse analyzed in Otis et al. (1978, Wildlife Monographs62, 93) is given for illustration. [source] Maternal factors and the probability of a planned home birthBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2005S. Anthony Objectives In the Netherlands, approximately one-third of births are planned home births, mostly supervised by a midwife. The relationship between maternal demographic factors and home births supervised by midwives was examined. Design Cross-sectional study. Setting Dutch national perinatal registries of the year 2000. Population All women starting their pregnancy care under the supervision of a midwife, because these women have the possibility of having a planned home birth. Methods The possible groups of birth were as follows: planned home birth or short stay hospital birth, both under the supervision of a midwife, or hospital birth under the supervision of an obstetrician after referral from the midwife during pregnancy or birth. The studied demographic factors were maternal age, parity, ethnicity and degree of urbanisation. Probabilities of having a planned home birth were calculated for women with different demographic profiles. Main outcome measure Place of birth. Results In all age groups, the planned home birth percentage in primiparous women was lower than in multiparous women (23.5%vs 42.8%). A low home birth percentage was observed in women younger than 25 years. Dutch and non-Dutch women showed almost similar percentages of obstetrician-supervised hospital births but large differences in percentage of planned home births (36.5%vs 17.3%). Fewer home births were observed in large cities (30.5%) compared with small cities (35.7%) and rural areas (35.8%). Conclusions This study demonstrates a clear relationship between maternal demographic factors and the place of birth and type of caregiver and therefore the probability of a planned home birth. [source] Anomalously Low Probabilities for Rotational Excitation in HD,Surface Scattering,CHEMPHYSCHEM, Issue 5 2006Antonio, iber Dr. The H2,Cs surface interaction potential is directly investigated by scattering a rotationally cold beam of HD molecules from a Cs surface (see angular distribution diagram). The probability of rotational excitation is two orders of magnitude smaller than for Cu and other metal surfaces. Coupled channel calculations interpret the results, and the anomalous behaviour is linked to the peculiarities of the closed-shell alkali surface interactions. [source] Participation and Impact of Poverty-oriented Public Works Projects in Rural MalawiDEVELOPMENT POLICY REVIEW, Issue 2 2002Ephraim W. Chirwa This article reports on factors influencing participation in the poverty-oriented public works programme in rural Malawi and analyses the determinants of the revealed positive socio-economic impact among the participants. The programme targets poor households through self-selection by offering a wage below the official minimum for rural areas. The empirical results show that most participants are poor and with little education. Probability of particpation is higher for members of female-headed households and households with longer periods of food insecurity, excess supply of labour, few assets and reservation wages below the wage offered in the programme. Taking account of selectivity bias, the impact of the programme increases with the gender (female) of participants and the numbers per household participating. [source] Probability of walking, wheeled mobility, and assisted mobility in children and adolescents with cerebral palsyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 1 2010ROBERT J PALISANO Aim, Our aim was to describe how the probability of walking, wheeled mobility, and assisted mobility changes with environmental setting and age in children and adolescents with cerebral palsy (CP). Method, The parents of a population-based sample of 642 children and adolescents (360 males, 282 females; age range 16mo,21y) reported their children's mobility at home, school, and outdoors at 6- or 12-month intervals a mean of 5.2 times. Generalized mixed-effects analyses were used to model the probabilities. Results, By age 3 years, children with motor function classified as level I according to the Gross Motor Function Classification System (GMFCS) walked in all three settings. Children/adolescents classified as level V used assisted mobility, with a small number using wheeled mobility. In the case of children classified as GMFCS level II, the probability of walking varied with the environmental setting, which, at age 18, is outdoors 90% of the time. Among children classified as GMFCS level III, the probability of walking was highest at age 9 at school (68%), and at age 18 was approximately 50% in all three settings. Among children/adolescents rated as GMFCS level IV, the probability of wheeled mobility increased with age and, at age 18, 57% of mobility took place outdoors. Interpretation, The results provide evidence that age and environmental setting influence method of mobility of children/adolescents with CP. The method that is preferred in one setting may not be preferred in another setting or at another age. [source] ORIGINAL ARTICLE: Probability of emergence of antimalarial resistance in different stages of the parasite life cycleEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 1 2009Wirichada Pongtavornpinyo Abstract Understanding the evolution of drug resistance in malaria is a central area of study at the intersection of evolution and medicine. Antimalarial drug resistance is a major threat to malaria control and directly related to trends in malaria attributable mortality. Artemisinin combination therapies (ACT) are now recommended worldwide as first line treatment for uncomplicated malaria, and losing them to resistance would be a disaster for malaria control. Understanding the emergence and spread of antimalarial drug resistance in the context of different scenarios of antimalarial drug use is essential for the development of strategies protecting ACTs. In this study, we review the basic mechanisms of resistance emergence and describe several simple equations that can be used to estimate the probabilities of de novo resistance mutations at three stages of the parasite life cycle: sporozoite, hepatic merozoite and asexual blood stages; we discuss the factors that affect parasite survival in a single host in the context of different levels of antimalarial drug use, immunity and parasitaemia. We show that in the absence of drug effects, and despite very different parasite numbers, the probability of resistance emerging at each stage is very low and similar in all stages (for example per-infection probability of 10,10,10,9 if the per-parasite chance of mutation is 10,10 per asexual division). However, under the selective pressure provided by antimalarial treatment and particularly in the presence of hyperparasitaemia, the probability of resistance emerging in the blood stage of the parasite can be approximately five orders of magnitude higher than in the absence of drugs. Detailed models built upon these basic methods should allow us to assess the relative probabilities of resistance emergence in the different phases of the parasite life cycle. [source] Lottery Expenditures in Canada: Regional Analysis of Probability of Purchase, Amount of Purchase, and IncidenceFAMILY & CONSUMER SCIENCES RESEARCH JOURNAL, Issue 1 2001Mohamed Abdel-Ghany This article has two purposes: First, to examine the effect of household characteristics on lottery expenditures in six regions of Canada using a double hurdle model to distinguish between the decision to play and the decision of how much to spend. Second, to estimate the incidence of lottery expenditures. Using the 1996 Canadian Family Expenditure Survey, the results portray the profile of households that have the probability of becoming participants in lottery play as well as the profile of households that spend more on lottery purchases. Lottery expenditures are found to be regressive in all regions. [source] Temporal dynamics and nestedness of an oceanic island bird faunaGLOBAL ECOLOGY, Issue 4 2006Ermias T. Azeria ABSTRACT Aim, To examine temporal variation in nestedness and whether nestedness patterns predict colonization, extinction and turnover across islands and species. Location, Dahlak Archipelago, Red Sea. Method, The distributions of land birds on 17 islands were recorded in two periods 30 years apart. Species and islands were reordered in the Nestedness Temperature Calculator, software for assessing degrees of nestedness in communities. The occupancy probability of each cell, i.e. species,island combinations, was calculated in the nested matrix and an extinction curve (boundary line) was specified. We tested whether historical and current nested ranks of species and islands were correlated, whether there was a relationship between occupancy probability (based on the historical data) and number of extinctions or colonizations (regression analyses) and whether the boundary line could predict extinctions and colonizations (chi-square analyses). Results, Historical and current nested ranks of islands and species were correlated but changes in occupancy patterns were common, particularly among bird species with intermediate incidence. Extinction and turnover of species were higher for small than large islands, and colonization was negatively related to isolation. As expected, colonizations were more frequent above than below the boundary line. Probability of extinction was highest at intermediate occupancy probability, giving a quadratic relationship between extinction and occupancy probability. Species turnover was related to the historical nested ranks of islands. Colonization was related negatively while extinction and occupancy turnover were related quadratically to historical nested ranks of species. Main conclusions, Some patterns of the temporal dynamics agreed with expectations from nested patterns. However, the accuracy of the predictions may be confounded by regional dynamics and distributions of idiosyncratic, resource-limited species. It is therefore necessary to combine nestedness analysis with adequate knowledge of the causal factors and ecology of targeted species to gain insight into the temporal dynamics of assemblages and for nestedness analyses to be helpful in conservation planning. [source] Revised Estimates for Probability of Successful Outcome of Pregnancy After Sumatriptan ExposureHEADACHE, Issue 3 2004Anthony W. Fox MD No abstract is available for this article. [source] The rapid spread of invasive Eurasian Collared Doves Streptopelia decaocto in the continental USA follows human-altered habitatsIBIS, Issue 3 2010IKUKO FUJISAKI Understanding factors related to the range expansion trajectory of a successful invasive species may provide insights into environmental variables that favour additional expansion or guide monitoring and survey efforts for this and other invasive species. We examined the relationship of presence and abundance of Eurasian Collared Doves Streptopelia decaocto to environmental factors using recent data from the North American Breeding Bird Survey to understand factors influencing its expansion into the continental USA. A zero-inflated Poisson (ZIP) model was used to account for excess zero observations because this species was not observed on the majority of survey routes, despite its large geographical range. Model fit was improved when we included environmental covariates as compared with the null model, which only included distance from the route where this species was first observed. Probability of zero count was positively related to the distance from the first route and road density and was inversely related to minimum temperature and distance to coast. Abundance of the species was positively related to road density and was inversely related to annual precipitation and distance to coast. Random intercept by land-cover type also improved model fit. Model fit was improved with the ZIP model over the standard Poisson model, suggesting that presence and abundance of this species are characterized by different environmental factors. However, overall low accuracy of model-predicted presence/absence and abundance with the independent validation dataset may indicate either that there are other explanatory factors or that there is great uncertainty in the species' colonization process. Our large-scale study provides additional evidence that the range expansion of this species tends to follow human-altered landscapes such as road and agricultural areas as well as responding to general geographical features such as coastlines or thermal clines. Such patterns may hold true for other invasive species and may provide guidelines for monitoring and assessment activities in other invasive taxa. [source] | ||||||||||||||||||||||||||||||||||||||||